Prescribed Burns as a Tool to Mitigate Future Wildfire Smoke Exposure: Lessons for States and Rural Environmental Justice Communities

Abstract

Smoke from wildfires presents one of the greatest threats to air quality, public health, and ecosystems in the United States, especially in the West. Here we quantify the efficacy of prescribed burning as an intervention for mitigating smoke exposure downwind of wildfires across the West during the 2018 and 2020 fire seasons. Using the adjoint of the GEOS‐Chem chemical transport model, we calculate the sensitivities of population‐weighted smoke concentrations in receptor regions, including states and rural environmental justice communities, to fire emissions upwind of the receptors. We find that the population‐weighted smoke exposure across the West during the September 2020 fires was 44 μg/m3 but would have been 20%–30% greater had these wildfires occurred in October or November. We further simulate a set of prescribed burn scenarios and find that controlled burning interventions in northern California and the Pacific Northwest could have reduced the population‐weighted smoke exposure across the western United States by 21 μg/m3 in September 2020, while doing so in all other states would have reduced smoke exposure by only 1.5 μg/m3. Satellite records of large, prescribed burns (>1,000 acres, or 4 km2) reveal that northern California and western Oregon conducted only seven such prescribed fires over a 6‐year period (2015–2020), even though these regions have a disproportionate impact on smoke exposure for rural environmental justice communities and population centers across the West. Our analysis suggests that prioritizing northern California and the Pacific Northwest for prescribed burns might mitigate future smoke exposure.

Prescribed fire placement matters more than increasing frequency and extent in a simulated Pacific Northwest landscape

“…As greater attention is paid to public health issues stemming from long-duration hazardous air quality events during wildfire season, prescribed fire provides an opportunity to distribute emissions throughout the year when smoke may be regulated and more manageable due to more ideal burning conditions (D'Evelyn et al, 2022). Furthermore, implementing prescribed burns in southwest Oregon and northern California during these conditions may mitigate widespread and long-term smoke exposure to communities across the western United States (Kelp et al, 2023).…”

Estimated impacts of forest restoration scenarios on smoke exposures among outdoor agricultural workers in California

“…Prescribed burns are increasingly being implemented to restore more natural fire regimes and reduce extreme wildfire risk across the western U.S. (Ryan et al 2013, Hessburg et al 2015, Stephens et al 2020. These fuel treatments have the potential to reduce smoke exposures from wildfires, but also contribute to hazardous air pollution themselves (Ravi et al 2018, Burke et al 2021, D'Evelyn et al 2022, Kelp et al 2023. Spatiotemporal differences in smoke exposures from wildfires and prescribed burns may have implications for outdoor agricultural workers, approximately 25% of whom are seasonally employed during the growing and harvesting seasons, which often overlap with peak wildfire smoke season (i.e.…”

Health Impacts of Future Prescribed Fire Smoke: Considerations From an Exposure Scenario in California

“…As the use of prescribed burning increases, understanding how smoke emissions and the corresponding health impacts compare to past levels can inform future mitigation efforts, fire and land management decisions, and public health planning. Recent studies have begun to characterize differential PM 2.5 impacts between wildfire and prescribed fire in the Western US (EPA, 2021;Kelp et al, 2023). However, few epidemiological studies have investigated health effects specifically attributed to prescribed fire smoke (Afrin & Garcia-Menendez, 2021;EPA, 2021;Huang et al, 2019;Prunicki et al, 2019).…”

“…The stewardship agreement established a framework for forest management agencies to greatly expand the use of prescribed fire across California's landscape. Current goals aim to treat 400,000 to 500,000 acres of lands with beneficial fire per year, a significant increase from previous years' estimates of approximately 100,000 acres of prescribed fire per year, which have been rising more recently (California Wildfire & Forest Resilience Task Force, 2022;Kelp et al, 2023;LAO, 2022). Prescribed and cultural burns are also conducted by local entities, such as tribal governments and private landowners (California Wildfire & Forest Resilience Task Force, 2022).…”